1. Field of the Invention
Embodiments of the present invention relate generally to a temperature detection circuit for a semiconductor device. More particularly, embodiments of the invention relate to a digital temperature detection circuit adapted to output a digitized reading of the internal temperature of the semiconductor device.
A claim of priority is made to Korean Patent Application No. 10-2005-109811, filed Nov. 16, 2005, the disclosure of which is hereby incorporated by reference in its entirety.
2. Description of Related Art
Temperature detection circuits are commonly included in semiconductor devices to detect the devices' internal temperature. Detecting the internal temperature of a semiconductor device can be important for a variety of reasons. For example, the internal temperature can alter the way the device's components work, or even cause the components to fail, and therefore a detected temperature can be used to either adapt the device's behavior to the changed temperature, or to somehow prevent the failure from occurring.
One example of how the internal temperature can affect a device's operating characteristics is provided by a self-refresh operation of a dynamic random access memory (DRAM). The self-refresh operation refreshes the logic state of memory cells in the DRAM to keep any data stored therein from fading. The required frequency of the self-refresh operation is temperature dependent. For example, at higher temperatures, stored information tends to fade more quickly. As a result, the frequency of the self-refresh operation can be increased if the internal temperature of the DRAM is detected to rise. By maintaining the self-refresh frequency at an appropriate level, power consumption in the semiconductor device can be preserved.
In general, a temperature detection circuit for a semiconductor device is included as part of the device. The temperature detection circuit typically detects the internal temperature of the device by comparing the temperature with a predetermined temperature threshold, which is established as part of the device's design. The temperature detection circuit produces a temperature detection signal with a logic state determined by the value of the on comparison results. In a so-called “digital temperature detection circuit”, an n-bit temperature detection signal is generated by comparing the internal temperature with 2n threshold temperatures.
Unfortunately, conventional digital temperature detection circuits can be inaccurate for at least a couple of reasons. First, there is often a gap between the theoretical threshold temperature that a device is designed to have and the device's actual threshold temperature. The gap can result from a variety of factors such as different conditions in a manufacturing process. Second, in conventional digital temperature detection circuits, variation in the output data of the detection circuit may not correspond precisely with variation in the internal temperature. For example, a change of 1° C. in the internal temperature may not consistently result in a change of “1” in the output data.
Variation in the output data of a digital temperature detection circuit due to a change of 1° C. in the internal temperature of a semiconductor device is referred to as a “response interval” of the digital temperature detection circuit. In some instances, the response interval of a digital temperature detection circuit may simply be a linear function of the change in temperature. In other cases, however, the response interval may be a non-linear function. In any case, however, where the response interval is not clearly indicative of changes in the internal temperature, it may be difficult for a user to read the output of the temperature detection circuit. For example, a change of 1° C. in the internal temperature of a semiconductor device may result in a change of 0.4 or 1.4 in the output data of the digital temperature detection circuit.